The well-known seasonal drift of influenza virus antigenicity accounts for the absence of long-term immune protection in previously infected individuals. The hemagglutinin (HA), a trimeric surface glycoprotein that binds the viral receptor and promotes fusion and penetration from low-pH endosomes, is the principal surface antigen on influenza virions. HA presents conserved as well as variable epitopes, but neutralizing antibodies against the latter dominate the response to immunization and infection.
Accordingly, there is a need for developing broadly neutralizing therapeutics that can effectively treat or prevent drifted strains of influenza.